March 29

1974: The first flyby of the planet Mercury takes place. Mariner 10 was a robotic space probe launched by NASA on November 3, 1973. The mission was to pass by Venus and Mercury and perform experiments to get data to help with future projects. The science team was led by Bruce C Murray and the Jet Propulsion Laboratory (JPL). The mission was the first to use interplanetary gravitation for a slingshot maneuver where Venus was used to bend the flight path into Mercury’s path. It was also the first spacecraft to use solar pressure as a means of flight control.

Mariner 10 performed seven different experiments and six of these had dedicated equipment with which to perform the task. There had been 46 submissions for hoped for experiments and JPL selected these seven based on maximizing scientific discovery while remaining in the budget guidelines. The total cost of the experiments was $12.6 million, about 12% of the total budget of the mission. Another consideration was the weight of the spacecraft and all equipment. Mariner 10 weighed in a 1,109 pounds at liftoff which took place at 12.45 Eastern Time on November 3 where it was put into a parking orbit. When it reached the correct spot, another burn pushed the craft out of the Earth Moon system.

The three month trip to Venus proved less than smooth sailing. Several technical difficulties arose and one problem would be fixed only to have another one crop up. Mariner 10 passed Venus on February 5, 1974 with the closest approach being 3,585 miles from the planet. She was the twelfth spacecraft to reach Venus and the first to send images back to Earth. As the spacecraft circled Venus and using the gravity assist, a new course was set and her speed dropped from 82,785 mps to 72,215 mph, allowing for an elliptical orbit around the Sun to intersect Mercury’s orbit.

Mariner 10 flew by Mercury three times. On this day, at 20.47 UT at a range of 437 miles, she passed on the shadow side of the planet. The first time an Earth ship went to visit the small Sunside planet. Mariner 10 made one trip around the Sun while Mercury made two and then passed again on September 21, this time at a more distant range of 29,869 miles. NASA lost roll control in October, but there was still a third encounter with Mercury. The closest and last pass took place on March 16, 1975 at a distance of 203 miles. The maneuvering gas was nearly gone but tests were continued until March 24 when the final nitrogen gas ran out. It is presumed Mariner 10 is still orbiting the sun but it was decommissioned when the nitrogen gas was gone.

All the traditional STEM fields, the science, technology, engineering, and math fields, are stoked when you dream big in an agency such as NASA. – Neil deGrasse Tyson

Many of us in Congress have been calling on the Administration to articulate a bold mission for NASA. It seems that the President is answering that call. I wholeheartedly support his vision for going back to the moon, and from there to worlds beyond. – Sheila Jackson Lee

NASA is an engine of innovation and inspiration as well as the world’s premier space exploration agency, and we are well served by politicians working to keep it that way, instead of turning it into a mere jobs program, or worse, cutting its budget. – Bill Nye

To me, NASA is kind of the magical kingdom. I was sort of a geek, and you go there, and there are just these wondrously strange things and people. – Mary Roach